Conventionally, ion selective electrodes have been used for measuring concentrations (or activities) of particular species of ions in a test solution, for example, for measuring concentrations (or activities) of particular species of ions such as Na ions, K ions, and Cl ions in a test solution such as serum used in a test room or the like in a hospital. Measurement using the ion selective electrodes includes a wet method and a dry method. For the wet method, a flow-type ion selective electrode device is generally used. In the flow-type ion selective electrode device, an ion selective electrode using an ion sensing film sensitive to particular ions and a reference electrode using a reference electrode film such as a silver/silver chloride (Ag/AgCl) electrode are provided in a flow path through which a test solution (sample) flows. The flow-type ion selective electrode device measures a potential difference (electromotive force difference) generated between the ion selective electrode and the reference electrode, and thereby measures the concentration of the particular ions in the test solution (for example, see Patent Document 1 and Patent Document 2). For the dry method, a method using an ion selective electrode in a film form has been proposed (for example, see Patent Document 3).